Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
Known surgical staplers include an end effector that simultaneously makes a longitudinal incision in tissue and applies lines of staples on opposing sides of the incision. The end effector includes a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members supports a staple cartridge that has at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument commonly includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
Different types of surgical staplers suitable for endoscopic applications are known. For example, on type of surgical stapling instrument is configured to operate with disposable loading units (DLU's) that are constructed to support a staple cartridge and knife assembly therein. Once the procedure is completed, the entire DLU is discarded. Such instruments that are designed to accommodate DLU's purport to offer the advantage of a “fresh” knife blade for each firing of the instrument. Examples of such surgical stapling apparatuses and DLU's are disclosed in U.S. Pat. No. 5,865,361 to Milliman et al., the disclosure of which is herein incorporated by reference in its entirety.
Prior surgical stapling apparatuses, such as those disclosed in U.S. Pat. No. 5,865,361, suffer from the inability to be fired in thicker tissues (e.g., tissues with thicknesses greater than 3.5 mm) due to the increased loads applied to their firing systems. Such increased loads can, for example, increase the likelihood that the firing system will fail when the blade is still in the anvil and may therefore require that the tool assembly thereof be cut off of the tissue which may lead to serious injury consequences for the patient.
Thus, there is a need for a disposable loading unit that can be easily opened in the event that the blade becomes jammed as it is driven through the tissue that is clamped in the unit.